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January 18, 2020 02:48
RiceThe first double haploid lines were obtained in the anther culture more than 50 years ago, but so far their production remains more art than a well-established technology. There are a huge number of articles with conflicting information, both on preliminary processing of anthers and medias that determine the highest yield of regenerants, despite the fact that the relevance of research in this area is difficult to overestimate. Double haploid (DH) lines are used: For increasing efficiency of traditional breeding; obtaining populations of DH lines used in several stages of fixing heterosis effect (to remove semi-lethal genes, as well as homozygotization of material) and so on. The objective of the study is to investigate the efficiency of media for producing DH lines in anther culture of hybrids between Russian and foreign varieties. The anthers of 67 hybrid combinations, both interspecific and intraspecific hybrids, were used. 30-50 anthers were planted on Petri dish (6 сm). After formation of callus (size varied from 2 to 10 mm) on the medium for dedifferentiation, they were transferred to MS medium for regeneration. Plants from 5 cm in size were transferred to the root formation medium. We study the effectiveness of nutrient media, which are derivatives of N6, but with a different hormonal composition; and С, RZ media, the salt content was also changed. Medias RZ and C did not reliably differ in callus yield; the rest were reliably inferior to them in this trait. Therefore, to increase the yield of callus, a higher content of salts of KNO3, KH2PO4, MgSO4 • 7H2O, MnSO4 • 4H2O, ZnSO4 • 7H2O, H3BO3, CaCl2 • 2H2O vitamins is necessary. However, their hormonal composition is different. If the RZ medium contains naphthylacetic (NAA) and dichlorophenoxyacetic acids ( 2,4-D), then C is only 2,4-D. N6-based media, N6a and N6б contain only one auxin as well as C. In the study, the best results were shown by option with content of both hormones at a concentration 2 mg / l NAA and 1 mg/l 2,4-D. The results showed a significant positive effect of increasing iron (FeSO4 x 7 H2O) concentration (55.6 mg / L) both on callusogenesis and plant regeneration. In standard recipe of all the media used in the work, its concentration is 27.8 mg / l. To stimulate somatic embryogenesis, the media were modified also by the addition of abscisic acid (ABA) and silver nitrate AgNO3. Studies have shown that somatic embryogenesis is stimulated in many genotypes when using ABA in combination with cytokinins. Callusogenesis and regeneration in the considered combinations had maximum values at AgNO3 concentration 2 mg/l and; 1 mg/l ABA for the of most of the studied hybrids.
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Posted January 18, 2020 02:48
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September 4, 2019 06:05
Different microbiome and Bacillus thuringiensis diversity and dynamics of field soils of sole rain fed rice, and deep/shallow water rice-fish cultivation systems of National Rice Research Institute was assessed to enrich knowledge on functionalities of active microbial guilds of aforementioned micro-ecologies. Diversity and dynamics (x105 cfu/g soil, approx.) of microbial guilds viz. heterotrophs (1.04-7.87), spore formers (0.37-0.99), Gram negative bacteria (0.87-9.44), asymbiotic N2 fixers (0.10-0.17), nitrifiers (0.04-0.38), denitrifiers (0.09-0.38), spore crystal formers (0.003-0.02), actinobacteria (0.004-0.005) and fungi (0.003-0.01), as well as, indices (0.07-0.19 x 10-2) of spore-crystal forming bacteria i.e. Bacillus thuringiensis (Bt) were highly diverse in rain fed rice and deep/shallow water rice-fish farming field soils. Four spore-crystal forming bacterial isolates viz. TB426 and 432 of rice field, and TB436 of deep water rice-fish and TB442 of shallow water rice-fish farming field soils were diverse in phenotypic characters, antibiotic/salt (6–11% NaCl) tolerance, crystal composition (bipyramidal but variable sizes) etc. The Bt isolates (Bts) had 62.10-76.87 kbp genomic DNA (gDNA) and single plasmid (24.33- 42.50 kbp). The Bts (TB 426/432) had 12-14 cellular proteins (9.88-540.7 kDa). Phenotypic identities of TB426 and 432 were Bacillus thuringiensis (Bt) var. galleriae, TB436 was Bt var. thompsoni/coreanensis and TB442 was Bt var. dendrolimus/sotto. The results proved structural and functional diversity of Bt population in NRRI rice soils of different micro-ecologies. The resident Bt with different toxin composition would be potent natural biocide and can be exploited for suppression of different rice field pests to sustain productivity.
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Posted September 4, 2019 06:05